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Friday, April 29, 2011

The advantages and disadvantages of vector and raster data for GIS,

List advantages and disadvantages of vector and raster data for GIS. What kind of applications would each be most suited to?

Advantages of the raster model :

• A simple data structure—a matrix of cells with values, representing a coordinate, and sometimes linked to an attribute table.
• A powerful format for intense statistical and spatial analysis.
• The ability to represent continuous surfaces and perform surface analysis.
• The ability to uniformly store points, lines, polygons, and surfaces.
• Capability to perform faster overlays (than vector datasets) with complex data.
• The same cell-based structure is used to represent all feature types; therefore, all feature types may be treated the same. This uniform structure allows you to combine a variety of geographic features in one geoprocessing operation (for example, query, overlay, or expression). You can combine a surface (elevation) with area features (forestry), linear features (rivers and roads), and point features (wells) in the same analysis.
• The ability to compress the datasets using either a lossy or lossless compression.
• Compatible with remote sensing images and all results images of spatial data scanning.
• The application software is cheaper.

Disadvantages of the raster model :

• Inherent spatial inaccuracies due to the cell-based feature representation.
• Datasets can be very large.
• Projection and transformation cooordinat is not easily.
• Difficult in representation topology connections.

Advantages of the vector model :

• Need a small space or place for storage data (disc).
• One layer can be connected with or many attribute for saving the space of storage data.
• Easily makes connection between topology and network.
• Have a high spatial resolution.
• Graphic representation spasial data closely likes man-handed map.
• Very good in correction limits, apparent and clear for making administration maps and owned-lands.
• Easily for making projection and coordinates transformation.

Disadvantages of the vector model :

• Have a complex data structures.
• Data not easily for manipulates.
• Users cannot created owned programs for applications needed. In this case, a complex of the vector data structure and analysis and function procedures needs high capability because its more difficult and complicated— users must buy a software because of expensive technology.
• Needs a long time only for all the process. Vector data often out-of-date.
• Not compatible with remote sensing images data.
• Needs more an expensive software and hardware.
• Overlay vector layers with simultant needs a long time.